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HIV prevention research will have to focus on antiretroviral drugs after both a vaccine and a microbicide failed in trials, say health experts.

The Lancet published the results of a failed trial of a vaginal microbicide gel to protect women from HIV infection last week (6 December). Meanwhile, one of the most promising vaccine candidates was reported last month (13 November) to have failed to protect against the virus.

The microbicide Carraguard was assessed in a randomised trial involving around 6,000 sexually active, HIV-negative women in South Africa.

At the end of the two-year trial, there were 134 infections in the Carraguard group and 151 in the placebo group. Additionally, the microbicide was used in only 42 per cent of sex acts. The results were released last February (see 'Anti-HIV gel fails to prevent infection') and the study has just been published.

"It was a powerful trial, which was as well-conducted as possible," says Willard Cates, a researcher at Family Health International in North Carolina, United States, who wrote a commentary in The Lancet.

"But I think it's safe to say that Carraguard as a sole microbicide agent does not work," he told SciDev.Net. "It could be that when leveraged with another product, such as an antiretroviral, [Carraguard] could be effective. And that would be intriguing as the next level of trial."

Cates wrote that the next frontier for HIV-prevention research is the evaluation of antiretroviral drugs to prevent HIV.

In trials of the vaccine — developed by pharmaceutical company Merck — recipients had a higher rate of infection than the control group.

Omu Anzala, programme director at the Kenya AIDS Vaccine Initiative (KAVI), says this result will send them back to the drawing board as KAVI, like many other HIV research groups, has been developing vaccines using a similar method to that of the Merck vaccine.

"The Merck trial affected many other trials. It has been a real wake up call for HIV researchers all over. At KAVI, we may not proceed with the trials until we review [our research] to better understand [the] immunology and virology," he told SciDev.Net. 

Cates says the HIV prevention community has not lost hopes of finding a vaccine. But given the uncertain timeframe for its development, the community needs to consider preventing the disease through the use of a combination of different treatment methods.

This should include both behavioural and research interventions that can reinforce each other, he says. "We need ABC–Z — a full alphabet of HIV prevention. There is no magic bullet. Everything [individually] really only provides partial protection."

Link to microbicide summary in The Lancet

References

The Lancet 372, 1,932 and 1,977 (2008)

The Lancet 372, 1,881 (2008)

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